Understanding bitter tasteperception
The bitter taste perception of vegetables is influenced by an interaction between variants of taste genes and the presence of naturally occurring toxins in the vegetables, say scientists at the Monell Chemical Senses Center, Philadelphia, Pa.

Scientists have theorized that bitter taste evolved as a defense mechanism to detect potentially harmful toxins in plants. The research conducted by Monell scientists supports this by showing that variants of the bitter taste receptor TAS2R38 can detect glucosinolates, a class of compounds in plants that adversely affect the thyroid. Glucosinolates inhibit iodine uptake by the thyroid, increasing the risk for goiter and altering the levels of thyroid hormones. The thyroid converts iodine into thyroid hormones, which are essential for protein synthesis and regulation of the body’s metabolism.

For the study, 35 healthy adults were genotyped for the hTAS2R38 bitter taste receptor gene. The three genotypes were PAV/PAV (sensitive to the bitter-tasting chemical PTC), AVI/AVI (insensitive), and PAV/AVI (intermediate).The subjects rated the bitterness of various vegetables, some of which contained glucosinolate (watercress, broccoli, bok choy, kale, and turmip) and some did not (radicchio, endive, eggplant, and spinach). The subjects who had the PAV/PAV form of the receptor rated the glucosinolate-containing vegetables as 60% more bitter than did the subjects with the AVI/AVI form. The other vegetables were rated equally bitter by these two groups of subjects, and this demonstrates that variations in the hTAS2R38 gene affect bitter perception, specifically of foods containing glucosinolate toxins, according to the researchers.

"The sense of taste enables us to detect bitter toxins within foods, and genetically based differences in our bitter taste receptors affect how we each perceive foods containing a particular set of toxins," summarizes Paul Breslin, a sensory scientist at Monell and senior author of the research study.

The scientists say that this research provides a complete understanding of the individual differences in responses to actual foods at multiple levels: evolutionary, genetic, receptor, and perceptual.

New package design center at Clemson
Sonoco Products Co., Hartsville, S.C., has donated $2.5 million for the creation of a new institute at Clemson University. The Sonoco Institute of Packaging Design and Graphics at Clemson University will provide resources for students of the university to enhance their opportunities for careers in packaging, printing, and allied fields.

Research work within the institute will be in four categories: research, testing, and product development; training; student and faculty projects; and short courses and special programs.

The institute will promote consumer and environmentally superior packaging design development, printing-imaging technologies and printing-packaging systems to enhance the reusability, traceability, and sustainability of paperboard, film, and corrugated paperboard packages.

The funds will be used to help pay for construction of the facility and commitments of gifts-in-kind for technology support of the institute.

Fatty acids target diabetes
A researcher at Penn State University has shown that fatty acids found in dairy products have successfully treated diabetes in mice. The conjugated linoleic acids (CLAs) have also shown promising results in human trials and could perhaps lead to ways of potentially treating the disease without the use of synthetic drugs.

"The compounds are predominantly found in dairy products such as milk, cheese, and meat, and are formed by bacteria in ruminants that take linoleic acids—fatty acids from plants—and convert them into conjugated linoleic acids," says Jack Vanden Heuvel, Professor of Molecular Toxicology at Penn State’s College of Agricultural Sciences and Co-director of the university’s Center of Excellence in Nutrigenomics.

Researchers first become interested in CLAs when it was shown that they can inhibit a variety of cancers such as breast, skin, and colon in mice. Further research has shown the effects of CLAs on circulating cholesterol and inflammation. These effects are the same as the newest generation of synthetic drugs used to treat diabetes in humans.

These synthetic drugs trigger a set of protein receptors called PPARs. This turns the receptors "on" into an active form of the protein, which then interacts with DNA and regulates gene expression. This increases the enzymes that process fatty acids and also increases the tissues’ sensitivity to insulin.

Vanden Heuvel says that he wanted to investigate if CLAs used the same mechanism. The results of tests conducted on mice prone to type 2 diabetes showed that the mice had an improvement in insulin action and a decrease in circulating glucose and that the mechanism was similar to that of the drugs.

"Anti-diabetes drugs act the same way," says Vanden Heuvel. "They mimic the natural activators of the receptors by getting into the cell and interacting with the PPARs to regulate glucose and fat metabolism,".

Other promising results of human trials indicate that CLAs improve the body’s misregulation of insulin and lowers the level of glucose in the blood in people with type 2 diabetes.

Vanden Heuvel cautions that while CLAs show these promising benefits, the foods in which they are found (dairy and meat) contain other fatty acids such as trans fatty acids.

Gentle extraction of lycopene
A scientist with the U.S. Dept. of Agriculture’s Agricultural Research Service has discovered a method to gently extract the antioxidant lycopene from watermelon flesh and juice, ensuring it stays in its most natural form.

Chemist Wayne Fish says that this method is unlike any method currently used because it respects the watermelon’s cellular makeup. The lycopene that is found in fruits and vegetables is naturally packaged in tiny structures call chromoplasts. Fish’s method does not compromise the integrity of these delicate organelles or their thin, fragile membranes. This is important because he has found that lycopene left inside its protective membrane coat is more stable and boasts a longer shelf life.

The lycopene extracted from watermelon by this method can be processed into a powder, paste, or liquid useful as a nutritional supplement or food coloring. Currently, most lycopene formulations are made from tomatoes, particularly the juice, skins, and fleshy residue that remains after processing. Fresh watermelon contains more lycopene than fresh tomatoes, ounce for ounce. The method can also be used to extract lycopene from tomatoes, guava, rosehips, and pink grapefruit.

Fish also explains that the method he developed may provide growers with a new market for the watermelons that are discarded for being bruised, misshapen, or discolored. Anywhere from 15 to 25% of the watermelon crop in the United States is discarded because of these blemishes; however, since the defects do not affect the lycopene content of the fruit, they can be a valuable source of lycopene.

by Karen Banasiak,
Assistant Editor
[email protected]